Fix casing of function names.
diff --git a/Doc/api/concrete.tex b/Doc/api/concrete.tex
index 583a548..3b12b5c 100644
--- a/Doc/api/concrete.tex
+++ b/Doc/api/concrete.tex
@@ -3005,9 +3005,9 @@
or the abstract number protocol (including
\cfunction{PyNumber_Add()}, \cfunction{PyNumber_Subtract()},
\cfunction{PyNumber_Or()}, \cfunction{PyNumber_Xor()},
-\cfunction{PyNumber_InplaceAdd()}, \cfunction{PyNumber_InplaceSubtract()},
-\cfunction{PyNumber_InplaceOr()}, and \cfunction{PyNumber_InplaceXor()}).
-Note, \cfunction{PyNumber_InplaceSubtract()} is also useful clearing
+\cfunction{PyNumber_InPlaceAdd()}, \cfunction{PyNumber_InPlaceSubtract()},
+\cfunction{PyNumber_InPlaceOr()}, and \cfunction{PyNumber_InPlaceXor()}).
+Note, \cfunction{PyNumber_InPlaceSubtract()} is also useful clearing
clearing a set (\code{s-=s}).
\begin{ctypedesc}{PySetObject}